Modern dental chairs include mechanism for raising and lowering the chair and tilting the back of the chair. The patient generally enters the chair when the chair is positioned with the back upright and with the seat elevated to permit comfortable entry. After the patient sits in the chair, the dentist or technician (hereafter operator), operates the chair to move the patient into a position selected by the operator which is most convenient for the procedure to be undertaken. For many procedures the chair back is tilted so that the patient assumes a more supine position.
Patient comfort is an important consideration. The chair should be configured so that the patient is comfortable irrespective of the chair position. Another important design consideration is that the operating position for the operator should be as convenient and efficient as possible for the operator.
In modern dentistry, the operator, whether it is a dentist or assistant, often will sit on a stool adjacent the back of the dental chair and the most convenient position to have the patient in is where the patient's head is as close to the operator's lap as possible. Thus it is helpful if the chair back is as thin as possible so that the operator's legs may be positioned under the back of the chair and minimal chair back thickness separates the operator's legs from the supine patient.